Wing Fairings

(28,29 October 2006) This is one of those jobs which I have been dreading because the amount of detail given in the plans and instructions is tiny, yet if you get it wrong your mistakes are there for all to see. The Wing fairings are long flat pre-cut and pre-drilled lengths of sheet (Image 1 is the relevant drawing, image 2 shows the fairing lying loose in position). The sheet is thick and hard to manouver, so you need to be careful not to scratch it and the fuse and wing. There are a few predilled holes in the wing top sheet and corresponding fairing. The temptation is to cleco these in place and then just match drill the rest from top to bottom. BUT, as Dan Checkway alerts us, you need to think about the TWO holes which actually correspond to countersunk screws already in the wing (one on top in the wing main spar, and one underneath in the tank skin). It would be too easy to work your way around the fairing, match-drilling and clecoing only to find the last hole does not fit the tank csk screw.

In my preliminary efforts i tried to use duct tape (image 3). You can see that the fairing location isinsecure and the gap between faiing edge and fuse is relatively uneven. Had I match-drilled at this point I would have had a bad fit, and the two countersunk screws would have not matched the hole position underneath. Afer a bit of thought I came up with the following sequence which worked well for me.

  1. Remove blue plastic from fairings
  2. Insert top surface clecos where fairing and wing skins are pre-drilled
  3. Skipping the hole over a countersunk screw, match drill (3/32") one hole aft and one hole forward of these pre-drilled holes (image 4). The 'gap between fairing and fuse should be fairly even (it was for me)
  4. Remove all clecos from top skin/fairing (Image 5)
  5. Crawl underneath and find the fuel tank screw/nuplate pair corresponding to the last pre-drilled hole in the fairing. Carefully remove the csk screw.
  6. Drill out (#19) this fairing hole to size and insert the screw though the fairing hole. Attach fairing by tightening the screw until the sheet is secure but NOT pressing into the fairing (Image 6, fairing is yet to be dimpled).
  7. Stretch the fairing to the front, straight and around the wing tightly. Make sure nothing is interefering with it. Bend a nice corresponding shape around the leading edge. Use the leading edge rivet line as a reasonable guide to alignment
  8. Re-insert clecos at the top, one at a time. the first one will be difficult and you may need to tilt the cleco a little to get it in both holes. I found I needed about 1/2mm of "coaxing"
  9. The more clecos you insert, the easier it will be. You are stretching the fairing around the wing.

Now you are ready to match-drill the remaining holes 3/32", and then expand to #19 and dimple

When I did this, I was amazed at how much more even the fairing position and orientation was, compared with the initial duct tape efforts. Given that two of the pre-drilled holes correspond with existing countersunk screws, it is imperative NOT to just dive in and start match-drilling without having the screw underneath also secured.

By the way, this worked for me, but it might not work for you.. please treat this as information and advice only. In the end you and you alone are responsible for how your efforts turn out!!

plans - very little detail given on how..

a long strip of sheet which needs to be bent

Fairing is pre-drilled, but be careful. Uneven gap.

First drill out ONE hole and cleco. Gap is even

Then release clecos and crawl underneath

Drill out one hole for platenut screw

Carefully replace top clecos - it is not easy

Note gap is now even and fairing is tight

Once the fairing is located, a precision ruler is used to measure from the fuse side to the fairing trim line. The fairing need to be timmed to be between 3/16" and 4/16" from the fuse. I drew a line at 7/32" from the fuse (Image 1 below) all the way around on both fairings, and trimmed with my Wiss Snips. No worries. Next, a #19 drill is used to drill holes for countersunk screws and platenuts to locate these fairings. I am overly cautious, so I drilled each hole and inserted a proper-sized cleco, before moving on to the next hole. Eventually all the holes were drilled out, both fairing and wing skin. Image 3 shows 3/32" clecoes separating #19 holes, midway thru this process.

Measure where to trim the fairings

Relocate and drill out.....

to # 19 drill for AN 509 screws